Stabilized bath for deposition of copper by chemical reduction



U.S. Cl. 106-1 United States Patent ABSTRACT OF THE DISCLOSURESpontaneous precipitation of copper from an electroless copper platingsolution is prevented by the addition of small amounts of seleniumbearing organic or inorganic compounds in which the selenium is in theoxidation stage 1 or 2.

This invention relates to electroless copper plating, and particularlyto the stabilizing of an aqueous bath containing a source of copper ionsand a reducing agent capable of reducing the ions to. metallic copper onthe surface of an object immersed in the bath.

Processes for applying metallic coatings on diverse base materials inwhich the metals are precipitated from solutions by chemical reductionwithout external sources of current are gaining increasing acceptance.Methods of depositing copper by reduction have become increasinglyimportant during recent years because copper precipitates formed bychemical reduction are particularly suitable for producing conductivecoatings on plastic sheets and plates, for example, in the electronicindustry for the production of printed circuits.

The bath compositions for depositing copper by chemical reduction knownheretofore have the disadvantage of being quite unstable so that theyhave to be used in very high concentrations if a high rate of depositionis to be achieved, and have to be discarded after a single use.

It has become known to admix addition agents, particularlysulfur-bearing compounds to the baths in order to improve theirstability, but these stabilizing agents may be added only in smallamounts because higher concentrations strongly reduce the depositionrate of the metal or may even prevent deposition. As a furtherdisadvantage, it has-been found that some of the known stabilizingcompounds cause a dark discoloration of the copper layer. Because thesulfur-bearing compounds often have little resistance to alkalis,particularly at elevated temperatures, copper baths intended fordeposition by chemical reduction have not been capable heretofore ofbeing stabilized over extended periods in a satisfactory manner.

It has now been found that selenium-bearing compounds in which theselenium is at the oxidation stage minus one or minus two are capable ofstabilizing copper reduction baths over long periods even at highertemperatures.

The term oxidation stage, as employed herein, is to be understood to bethe so-called oxidation number or the charge value, that is, theelectric charge which an atom would have in a molecule composed solelyof ions.

It is a particular technical effect of these compounds that they permitbright copper layers of constant thickness to be deposited from suchbaths.

Patented Jan. 27, 1970 Suitable selenium compounds having an oxidationstage or degree of oxidation of minus one" are compounds of the formulawherein R and R may be identical or different and may be a monovalentmetal equivalent or an organic radical. Suitable selenium compoundshaving an oxidation stage of minus two are compounds of the formula:

wherein R and K, may be equal or different and may have the same meaningas R and R R also being hydrogen or the radical So Me, wherein Me is amonovalent metal equivalent.

Other suitable selenium compounds of the oxidation ,sta e minus two arethe selenonium com unds of the wherein R R and R, may be equal ordifi'erent, R and R being as defined above, R being an organic radical,and X being the radical of an acid.

Monovalent metal equivalents that may be considered are Na, K, Ca/ 2,Al/ 3, and the like; organic radicals may be aliphatic, cycloaliphatic,aromatic, and araliphatic radicals which may also be substituted and/ orinterrupted by one or more hetero atoms such as oxygen, nitrogen, orsulfur, and/ or one or more groups of hetero atoms such as well as thearacyl radical and the CN group.

Suitable substituents for the afore-mentioned organic radicals includehalogen atoms, such as chlorine, bromine, and others, hydroxyl radicals,alkyl radicals such as methyl, ethyl, and others, aryloxy radicals, suchas phenoxy and the like; alkoxy radicals such as methoxy, ethoxy, andthe like; acyloxy radicals, such as acetoxy and the like; the nitro andcyano radical; the carboxy and sulfo groups in the free form or in theform of their functional derivatives, such as esters or salts;heterocyclic radicals such as tetrahydrofuryl and the like, as well asthe radicals The usual acid radicals of the onium compounds may beemployed in the selenonium compounds, such as the radicals of theinorganic acids, preferablv of the hydrogen halides.

Copper baths which contain the compounds of the invention are suitablefor depositing copper layers on metals or suitably pretreated andactivated plastics while the copper baths are absolutely stable. Becauseof their particular stability, the baths do not require particularmaintenance and need not be renewed after each use. It is merelynecessary to replenish them for the losses caused by drag-out. Thecopper deposits from these baths are particularly decorative and aredistinguished by bright, salmon-colored metallic luster.

Compounds which may be employed according to the invention include thefollowing:

B. SELENIUM COMPOUNDS HAVING THE OXIDATION STAGE MINUS TWOC0ntinuedQua-011F000 CHOOCCHz-SeCHz-COOH 0-, m-, or p-ch1orophenylseifiiumceticacid.

3,4-dimethylphepyise1eniumacetic acid.

2,4-dimethylphenylseleniumacetic acid.

Benzylseleniumacetic acid.

Ethyiseleniumacetic acid.

Seleniumdiacetic acid.

Seleniumdipropionic acid.

Seleniumdibutyric acid.

Benzylseleniumbutyric acid.

Benzylseleniumundecanoic acid.

Sodium ethyiseleniumprbp'anesulionate.

Bis-(sodium sulfopropyl) selenide.

Dibenzylselenide.

Difurfurylselenide.

Bis-p-methylphenyl seienide.

Bis-p-nitrophenyl selenide.

Bis-3-pheny1prbpy1selenide.

Dipropyl-selenide.

Bis-(hydroxyethyl) -se1enide.

Sodium selenocyanate.

Potassium selenocyanate.

o, por m-nitrophenyl selenocyanate.

o-, mor p-methylphenyl selenocyanate.

p-Methoxyphenyl seienocyanate.

p-Ethyiphenyl selenocyanate.

B. SELENIUM COMPOUNDS HAVING THE OXIDATION STAGE MINUS TWOC0ntinued -oCHr-CHz-SeCN KO CILSPION @cm-swn @om-cm-cmswrq OzN-CHzSeCNp-Ethoxyphenyl selenocyanate.

Sodium 4-eyanoseleno-phenylsulfonete.

0-, mor p-ohlorophenyl selenocyanate.

2-nitro-4-ehlorophenyl selenoeyanate.

p-Carbmethoxyphenyl selenocyanate.

Potassium seleiiocyanoethane-sulionate.

Phenoxyethyl selenocyanate.

Furiuryl seienocyanate.

Benzyl seienocyanate.

Phenylpropyl selenooya'nate.

p-Nitrophenyl selenocyanate.

li-Naphthyl seienooyanate.

Phenyl seienocyanate.

Carboxymethyldimethyl-selenonium bromide Phenacyl-dimethyl-selenoniumbromide.

Dimethyl-selenetin dicarboxylic acid.

Triethyiselenonium iodide.

Tribenzyiselenonium chloride.

Dimethyl-benzyl selenonium bromide.

Triphenylselenonium chloride.

Tri-p-tolylselenonium chloride.

Compounds containing a group which renders them water soluble areparticularly suitable because they are readily dosed and are capable ofproviding lasting stability. Copper reduction baths containing one ormore of these compounds are extraordinarily durable.

Further to be singled out are the selenocyantes, particularly potassiumselenocyanate which are distinguished by excellent stabilizing abilityand by being capable of being prepared with relative ease.

Effective stabilizers according to the present invention which have anoxidation stage of minus two are also the compounds which may be formed,for example, by hydrolysis of the selenocyanates in an alkaline medium,that is, so-called selenoles of the formula Rr-SCH wherein R is asdefined above, or their metal salts.

The compounds mentioned above are known or may be prepared by methodsknown in themselves, as they have been described for the several classesof compounds, for example, in Methoden der Organischen Chemie (Methodsof Organic Chemistry), by Houben-Weyl, vol. 9 (1955), pages 937-947(preparation of selenocyanic acids), pages 972-1002 (preparation ofselenides), page 1034 (preparation of selenonium compounds), pages1086-1099 (preparation of diselenides), pages 1089- 1090 (preparation ofselenosulfates) PREPARATION OF COMPOUNDS OF CLASS A (Selenium compoundshaving a stage of oxidation of minus one) (a) Di- (potassiumsulfopropyl)-diselenide 10.7 g. potassium w-sulfopropylselenocyanate aredissolved in 80 ml. concentrated NH OH solution, and the solutionis'left to stand for two days at room temperature in an open container.It is then evaporated to dryness in a vacuum, and the residue isrecrystallized from methanol. Yield: 7.8 g.=81% of theory (whitecrystals).

(b) Dipotassium bicarboxyethyldiselenide 11 g. potassiumw-carboxyethylselenocyanate are dissolved in 80 ml. concentrated NH OHsolution, and the solution obtained is left to stand at room temperaturefor two days in an open container. The solution is evaporated todryness, and the residue is recrystallized from methanol. Yield: 6.2g.=65% of theory (white crystals).

(c) Dipotassium bis-carboxypropyl-diselenide 16 g. dipotassiumcarboxypropylselenosulfate are dissolved in boiling ethanol, andsufiicient iodine is added until the iodine color no longer disappears.The diselenide precipitating after cooling is filtered off with suctionand recrystallized from methanol. Yield: 6 g.=59% of theory (whitecrystals).

(d) Dipropyl diselenide 32 g. selenium are completely dissolved withheating in mixture of 16 g. sodium hydroxide and 25 g. sodiumformaldehyde sulfoxylate in 250 ml. water, and 40 g. propyl bromide arethen added slowly. After heating for one hour, the reddish brown colorof the solution disappears almost completely, and a heavy red oil isprecipitated and is taken up in chloroform. The solution is dried oversodium sulfate and fractionated. Yield: 65% of theory. HP. at 15 mm; Hg:103-104" C.

(e) Dibenzyl diselenide 10 g. benzyl chloride are shaken for about 6hours with a solution prepared by briefly heating minutes) precipitatedred selenium (6.5 g.) in aqueous 15% sodium hydroxide solution (100cmfi), the black layer is separated and extracted with boiling alcohol.Yield: 60% of theory. M.P. 91-92" C.

12 (f) Diphenyldiselenide 18.2 g. phenylselenocyanate are added to anaqueous solution containing 15 g. KOH, and the mixture is stirred forabout 5 hours. The selenocyanate is dissolved. The diselenide is slowlyprecipitated. It is recrystallized from petroleum ether. Yield: oftheory. M.P. 61-62 C.

Other diselenides may be prepared in an analogous manner.

PREPARATION OF COMPOUNDS OF CLASS B (Selenium compounds having a stageof oxidation of minus two) (a) Potassium butylselenosulfate 13 g. butylbromide are added to a freshly prepared solution of K SeSO containing 8g. selenium, and the mixture is refluxed while nitrogen is being passedtherethrough for about /2 hour until a sample does not precipitateselenium when acidified with glacial acetic acid. The aqueous solutionis evaporated to dryness and exhaustively extracted with ethanol. Theselenosulfate crystallizes in White crystals from the alcoholicsolution. Yield: 60% of theory.

Other alkylselenosulfates are obtained in an analogous manner.

(b) Potassium p-nitrobenzylselenosulfate 2.3 grams of finely powderedselenium were boiled with a solution of 6 grams potassium sulfite in 55ml. water for three quarters of an hour, and the hot solution wasfiltered to remove a small amount of residual undissolved selenium. 5grams p-nitrobenzyl chloride, dissolved in 50 ml. alcohol were thenadded, and the resulting turbid solution was refluxed over an openflame. The turbidity disappeared in a very short time, but a precipitatebegan to form after about 5 minutes. Heating was continued for tenminutes, and the contents of the flask were then cooled rapidly. Acopious precipitate consisting chiefly of potassium p-nitrobenzylselenosulfate, but containing a small quantity of p-nitrobenzyldiselenide and some potassium chloride, sulfate, and sulfite, wasthereby produced. The inorganic salts were removed by recrystallizingthe precipitate several times from 95% alcohol.

Other selenosulfates are prepared in an analogous manner.

(c) Phenylselenocyanate Aniline (9.1 g.), dissolved in dilute sulfuricacid (1:4), was diazotised at 3 C., with sodium nitrite (9.5 g.). Thesolution, made neutral to Congo paper with sodium acetate, was added tocold aqueous potassium selenocyanate (22 g.). The odor of an arylselenocyanate was at once produced, and the mixture, when subjected tosteam distillation after 15 hours, gave a pale yellow oil. After beingdried with calcium chloride, this boiled at 134 C. 10 mm. (yield: about50% ((1) Potassium selenocyanoacetate 13.3 g. potassium monochloroacetate were dissolved in a little water, and the solution was mixed with analcoholic solution of 14.4 g. KSeCN. After standing for two days, thesolution was evaporated to dryness, and the residue was extracted withethanol. Potassium selenocyanoacetate crystallizes from the alcohol.Yield: 60% of theory (white crystals).

(e) Potassium selenocyanopropanesulfonate 18.3 g. propanesultone,dissolved in 70 ml. acetone, are added drop by drop at about 50 C. to asolution of 21.6 g. KSeCN in 200 ml. acetone. The selenocyanate isprecipitated at once. It is filtered with suction after cooling. Theproduct obtained is analytically pure. Yield: 35.6 g=89% of theory.

Potassium selenocyanobutanesulfonate and potassium selenocyanopropionatemay be prepared in the same simple manner from butanersultone and KSeCN,and from propiolactone and KSeCN respectively.

(f) Potassium selenocyanate Method (a).7.9 g. selenium are added insmall portions with stirring to a solution of 9 g. KCN in 25 ml. water.The temperature is not to exceed 30C. A small amount of undissolvedselenium is removed by filtration.

Method (b).-A mixture of 210 g. (95%) potassium cyanide and 240 g.commercial gray selenium. is melted in a large porcelain evaporatingdish at 150 to 160C. on a sand bath or on an electric hot plate. Themelt is stirred with a porcelain spatula until all the seleniumdissolves. It is then permitted to cool slowly, with continuousstirring, in order to prevent caking during solidification.

The solidified melt is crushed to a fine powder and is immediatelydissolved in 1 l. of hot .acetone. A slow stream of carbon dioxide,dried over phosphorus pentoxide, is passed through the acetone solutionfor 2 hours. This treatment precipitates alkali metal hydroxides asinsoluble carbonates. The slime, consisting of carbonates and tellurium,is collected by filtration on a Buchner funnel and is washed with warmacetone. The filtrate is transferred to a distilling flask, andtwo-thirds of the acetone are distilled off. The residual solution ispoured into a beaker, where a large portion of the salt precipitates oncooling. The colorless needles are filtered and washed several timeswith anhydrous ether. Yield: 325 g. (75%).

NaSeCN is prepared in an analogous manner at 240- 260 C.

(g) n-Butylselenocyanate (h) Dibenzyl selenide 0.2. mol benzyl chloridewas added to 0.1 mol potassium selenide in a reaction-flask which wasthen placed on a steam-bath for about two hours while its contents wereagitated by a weak stream of hydrogen. The solution was cooled andacidified with hydrochloric acid, and the benzyl selenide was extractedwith ether. The compound, when recrystallized from absolute alcohol,melted (i)' Dipropyl selenide A mixture of sodium formaldehydesulfoxylate (90 g.; 0.76 mol), sodium hydroxide (70 g.; 1.75 mol),powdered selenium (25 g.; 0.32 mol), and water (300 ml.) was .heated toabout 50 C. and propyl iodide (67.5 ml.; 0.32 mol) was slowly added. Thereaction was vigorous and was completed by refluxing for 1-3 hours. Theselenide was isolated by addition of water and extraction with ligroin.Distillation yielded a pure product. Yield: 54%.

-' (j) Di-w-carboxyethyl selenide=Seleniumdipropionic acid 0.2. molw-bromobutyric nitrile dissolved in methanol are left to stand overnightwith 0.1 mol K Se. After removal of the KBr formed, the liquid is barelyacidified, the methanol is distilled oil, the residue is extracted withether, and the extract is dried over Na SO The ether is 14 evaporatedand the residue is recrystallized from CCl M.P. ,95 C.

The other di-fatty acid selenides are prepared in a correspondingmanner. The salts of 'carboxylic acids may be employed instead of thenitriles. Propanesultone, butanesultone, and propiolactone may beemployed respectively instead of the corresponding brominated fattyacids in preparing di-sulfopropyl selenide, disulfobutyl selenide, anddi-carboxyethyl selenide.

(k) Diphenyl selenide A solution of NaNO; in water was added dropwise toa mixture of aniline, HCl and ice, and the diazonium salt solution wasadded to an aqueous solution of K Se (prepared as described). An oilylayer separated from an aqueous layer. The aqueous solution wasdecanted, heated to boiling, and poured back on the oily layer. CHCI wasthen added, the mixture was filtered, and the organic layer wasdistilled. Yield:

(l) Phenylselenoglycolic acid Twenty grams of finely powdered seleniumwere added slowly to magnesium phenyl bromide prepared from 39 g.bromobenzene and -6 g. magnesium in dry ether. The mixture foamedstrongly and was cooled on ice, the reaction being afterwards completedby warming on a water-bath. The mixture was again cooled and poured overice and hydrochloric acid, whereby a small quantity of hydrogen selenidewas developed and red selenium precipitated. The ether layer wasextracted rapidly with 7 g. of caustic potash in 60 ml. water, and 100ml. ethanol were added to the aqueous solution together with a solutionof sodium chloroacetate. Heat was generated, and sodium glycolate wasprecipitated as a white powder. The reaction was completed on awater-bath, and the solution was evaporated to one-half its originalvolume, whereby sodium phenylselenoglycolate was crystallized in pinkishwhite plates.

Phenylselenoglycolic acid precipitated as a pale yellow oil whenhydrochloric acid was added to an aqueous solution of its colorless,recrystallized sodium salt. The acid dissolved in a large quantity ofboiling water, precipitating therefrom as a colorless oil, B.P. /75Omm., which became crystalline on standing for several days. M.P.=40 C.

The alkylselenoalkylcarboxylic acids, and the corresponding sulfonicacids, and the arylalkylselenoalkylcarboxylic acids and sulfonic acidsare prepared in the same manner. The corresponding selenopropyland-butylsulfonic acids and the corresponding selenopropylcarboxylic acidsare prepared in a particularly simple manner from the correspondingsalts of the selenoles and ropanesultone, butanesultone, andpropiolactone respectively.

(m) Triethylselenonium iodide A few colorless needles are formed after24 hours at room temperature in an equimolecular mixture of diethylselenide and ethyl iodide, and the entire mass solidifies in crystallineform after ten days. The triethylselenonium iodide which is stable incontact with air is washed with a little ether and dried.

(n) Dimethyl-selenetin-dicarboxylic acid Equivalent amounts ofseleniumdiacetic acid and seleniumchloroacetic acid are dissolved inwater, neutralized, and heated on a water bath for two hours. Aftercooling, the reaction mixture is acidified with sulfuric acid. Thereaction product, which gradually crystallizes, may be recrystallizedfrom water. M.P. about 177 C. Yield: about 50% of theory.

The arylalkylselenonium compounds and other alkylselenonium compoundsmay be prepared in an analogous manner.

(o) Triphenylselenonium chloride 30 g. (0.22 mol) anhydrous aluminumchloride are added to 87 g. (100 ml., 1.1 moles) benzene. The suspensionobtained is cooled in an ice bath, and 40 g. (0.13 mol) diphenylseleniumchloride are added in portions of about 1 g. over a period of 25minutes. The temperature should be below 10 C. prior to each addition toprevent dark discoloration of the product. When the addition ofdiphenylselenium chloride is completed, the reaction mixture is allowedto stand for three hours at room temperature, whereupon 200 ml. waterare added cautiously. The benzene layer is discarded, and the waterlayer is extracted three times with 50 ml. batches of chloroform. Thecombined extracts are evaporated to 40 ml., and the concentrate is mixedwith 120 ml. ether. A yellow oil precipitates and solidifies almost atonce to a powder. The yield is 30 g. (67% of the theoretical amount).

Other arylselenonium compounds are prepared in an analogous manner.

The compounds of the invention are added as stabilizers to copperreduction baths of otherwise conventional composition in concentrationsof about 0.0001 g./liter to 0.300 g./liter, the compounds of theinvention being employed singly or in combination with each other. Thestabilized copper reduction baths also may contain the usualingredients, that is, copper salts, reducing agents, bufieringcompounds, complexing agents, as well as wetting agents and brighteners,and the like.

Objects made, for example, of metals, plastics, or other materials maybe copper coated in a manner known in itself by means of the copperbaths stabilized according to this invention.

For this purpose, the materials to be copper coated are immersed in theabove-described baths. Deposition is caused to take place at a bathtemperature of about 20 to 60 C. until the desired coating thickness 'isachieved. Copper plating periods of more than 20 minutes are usuallyunnecessary. It is advisable to mix the bath vigorously by means of astirrer in order to produce uniform copper layers.

Non-conductive materials, such as a plastics part, require a preliminarysurface treatment. This is performed in a manner known in itself, forexample, by chemical roughening of the surface by means of hotconcentrated sulfuric acid, and by chemical activation by means ofsolutions of stannous chloride, silver nitrate, or palladium dichloride.

It is a necessary prerequisite for stable baths that metals, in whosepresence copper deposits are formed, be absent. Vessels and containersmade of plastics, such as polyvinyl chloride, polyethylene, orpolypropylene, or lined with such plastics are therefore suitable forhandling and storage of the baths.

The desired deposition of copper coatings begins on metal surfaces or onsuitably prepared surfaces of materials not conductive in themselvesonly when the solutions are brought into contact with the metals ormetal nuclei.

The following examples illustrate a few of the stabilized copper bathsof the invention.

Example 1:

CuSO -H O g./l Disodium ethylene diaminetetraacetate g./l NaOH g./l 16Paraformaldehyde g./ l 4 Benzylseleniumacetic acid mg./l 2

Example 2:

CuSO -5H O g./l 20 Disodium ethylene diaminetetraacetate g./l NaOH g./l8 Paraformaldehyde g./l 12 p-Nitrophenylseleniumacetic acid mg./l 160 16Example 3:

CuSO '5H O g./l 5 Disodium ethylene diaminetetraacetate g./l 16 NaOHg./l 8 Paraformaldehyde g./l 16 p-Methylphenylseleniumacetic acid mg./l40 Example 4:

(311804 g./l Disodium ethylenediaminetetraacetate g./l 40 NaOH g./l 24Paraformaldehyde g./l 16 Phenylseleniumacetic acid mg./l 70 Example 5:

CUSO SHgO g./l Triethylenetetrarnine g./l 10 NaOH g./l l6Paraformaldehyde g./l 10 Potassiumselenocyanate mg./l 2

Example 6:

CuSO -5H O g./l 10 Triethylenetetrarnine g./l 8 NaOH g./l 16Paraformaldehyde g./l 16 Selenocyanoacetic acid mg./l 0.1

Example 7:

CuSO -5H O g./l 10 Disodium ethylenediaminetetraacetate g./l 20 NaOHg./l 12 Paraformaldehyde g./l 8 p-Nitrophenylselenocyanate -mg./l 1

Example 8:

CuSO '5H O g./l 10 Rochelle salt (potassium sodium tartrate g./l 10 NaOHg./] 24 Paraformaldehyde g./l 12 Selenocyanoacetic acid mg./l 3

Example 9:

CuSO -5H O g./l 10 Trisodium hydroxyethyldiamino-ethylene triacetateg./l 18 NaOH g./'l 12 Paraformaldehyde g./l 8 Selenocyanocetic acidmg./l 2

Example 10:

CuSO -5H O g./l 1O Disodium ethylenediaminetetraacetate g./l 20 NaOHg./l l6 Paraformaldehyde g./l 8 Carboxymethyl-dimethylselenonium bromidemg./l 200 Example 11:

CuSO -5H O g./l 10 Disodium ethylenediaminetetraacetate g./l- 20 NaOHg./l 16 Paraformaldehyde g./l 8 Phenylacyl-dimethylselenonium bromidemg./l Example 12: G./l. CuSO -5H O 10 Disodiumethylenediaminetetraacetate 20 NaOH l6 Paraformaldehyde 4 Di-(potassiumsulfopropyl -dise1enide 0.002

Example 13:

CuSO -5H O Disodium ethylenediaminetetraacetate 25 NaOH 8Paraformaldehyde l3 Di-(2,3-dihydroxypropyl) -diselenide 0.050

Example 14: G./l. Example 25: G./l. CUSO2'5H4O 8 C|.1S()45II2C) Disodiumethylenediaminetetraacetate 16 Disodium ethylenediaminetetraacetate 15Sodiumhydroxyde 8 Sodiumhydroxyde 15 Paraformaldehyde 15Paraformaldehyde 1O Dibutyldiselenide 0.020Potassium-(p-potassiumcarboxybenzyl)- selenosulfate 0.005 ExampleExample 26:

Q1504 20 C SO .5 0 15 Disodium ethylenediaminetetraacetate 35 1* 2 ["T".Sodiumhydroxyde 23 isodlum ethy enediammetetraacetate 20 Sodmmhydroxyde10 Paraformaldehyde Paraformaldehyde 10 Dlbenzyldlselemde 0'010Potassium (p-methoxy'benzyl)-selen0sulfate 0.0009

Example 16: v m 1e 27:

4' 2 12 15 'c :1s0 -5H 0 Tnefhylenedl'amme 12 Disodiumethylenediaminetetraacetate Sodlumhydroxyde 16 Sodiumhydroxyde 15Parafofmalehyqe 10 Paraformaldehyde 10 Potasslumdlselemde 0001 20Potassium-(p-cyanobenzyl)-selenosulfate 0.009

Example 17: Example 28:

CuSO 5H O 10 CuSO 5H O 25 Triethylenetetramine 8 Disodiumethylenediaminetetraacetate Sodiumhydroxyde 16 Sodiumhydroxyde 18Paraformaldehyde 16 25 Paraformaldehyde 19BiS-(4-CaTbOXYPheIIY1)'diselenide 0100Potassium-(p-bromobenzyl)-selenosulfate 0.150 Example 18: Example 29!CUSO2'5H4O CUSO4'5H2O Disodium ethylenediaminetetraacetate 20 30Trisodium hydroxyethyldiaminoethylene tri- Sodiumhydroxyde 12 acetate 118 Paraformaldehyde 15 NaOH 12Bis-(w-potassiumcarboxyl-decyl)-dise1enide 0.150 Paraformaldehyde 8Potassiumbutylselenosulfate 0.005 Example 19-. 10 Example 30:

CuSO 5H O Rochelle salt (potassium sodium tartrate) 24 4 2 v 10Sodiumhydroxyde 24 Rochelle salt (potassium sodlum tartrate) 24Paraformaldfihyde 2,2 i ififirgaia ag i2 i B18 potasslumsulfopropy dlsee 40 Potassiumoctylselenosulfate M20 Example 20: 1

cu s02 -sH. g;;3j.- 15 Trlsodlum hydroxyethyldlammo'ethylene tn' 19Disodium ethylenediaminetetraacetate 20 acetate g z i g Paraformaldehyde10 ara orma e e Bis-(w-potassiulnsulfopropyl)-di e1 id 0 0Potassium(phenoxyethyl)-selenosulfate 0.008

Example 32:

Example 21: CuSO -5H O 20 CuSO -5H O 10 Disodiumethylenediaminetetraacetate 25 Disodium ethylenediaminetetraacetate 20NaOH 12 Sodiumhydroxyde 16 Paraformaldehyde 12 Paraformaldehyde 9Potassium-(potassiumcarboxydecyl) -se1eno- Di-(4-sulfopheny1)-diselenide0'030 sulfate 0.015

Example 22: Example 33:

c s0 -5 0 10' g.' z 10 Disodium ethylenediaminetetraacetate 0 Disodlumethylenedlammetetraacetate 15 Sodiumhydroxyde 1 6 NaOH 8Paraformaldehyde 10 Paraformaldehyde 8 P 3 h d l 1 If 0 005Bis-(4-methoxyphenyl)-diselenide 0.010 otasslum( Y YP PY @1108 ateExample 34:

Example 231 01150 5111 0 s 4' 2 10 Disodium ethylenediaminetetraacetate10 Disodium ethylenediaminetetraacetate 20 NaOH 8 SQdiumhydroXyde 15Paraformaldehyde 8 Paraformaldehyde 9Potassium-(potassium-w-carboxypropyl)-se1e- Pofassiumselenosulfate 0.010nosulfate 5 Example 24: Example 35:

0150 SH O 12 CuSO SH O 10 Disodium ethylenediaminetetraacetate 21Disodium ethylenediaminetetraacetate 12 Sodiumhydroxyde 18 NaOH 10Paraformaldehyde 9 Paraformaldehyde 10 Potassiumbenzylselenosulfate0.040 Potassium (phenyl-propyl)-selenosulfate,0 0.009

Example 36: v G./l. CuSO -5H O l2 Disodium ethylenediaminetetraacetate15 NaOH 12 Paraformaldehyde 10 Potassium-dodecyl-selenosulfate 0.019

Example 37:

CuSO -5H O 15 Disodium ethylenediaminetetraacetate 25 Sodiumhydroxyde 19Paraformaldehyde 15 Bis-(p-nitro-benzyl)-diselenide 0.001

Example 38:

CUSO4 Disodium ethylenediaminetetraacetate 25 Sodiumhydroxyde 10Paraformaldehyde 13 Bis-(p-cyanobenzyl)-diselenide 0.0009

Example 39:

CuSO 51-1 20 Disodium ethylenedia'minetetraacetate 25 Sodiumhydroxyde 9'Paraformaldehyde 15 Bis-(p-carboxy-benzyl)-diselenide 0.005

Example 40:

CUSO4'5H2O Disodium ethylenediamine tetraacetate 30 Sodiumhydroxyde 23Paraformaldehyde 15 Bis-(p-bromobenzD-diselenide 0.010

Example 41:

CuSO SH O 19 Disodium ethylenediamine tetraacetate 25 Sodiumhydroxyde 20Paraformaldehyde 19 Bis-(3-hydroxy-propyl)-diselenide 0.030

Example 42:

CuSO H O 25 Disodium ethylenediaminetetraacetate 30 Sodiumhydroxyde 20Paraformaldehyde Bis-(B-phenoxy-ethyl)-diselenide 0.020

Example 43:

CuSO -5 0 10 Disodium ethylenediaminetetraacetate 20 Sodiumhydroxyde 12Paraformaldehyde Bis-(a-tetrahydrofurylmethyl)-diselenide 0.010

Example 44:

CuSO -5H O 15 Disodium ethylenediaminetetraacetate 25 Sodiumhydroxyde 15Paraformaldehyde 10 Bis-(cyclohexyl)-diselenide 0.008 Example 45:

CuSO -5H O Disodium ethylenediaminetetraacetate Sodiumhydroxyde 18Para-formaldehyde 15 Bis-(cyclopentyl)-diselenide 0.003

' What is claimed is:

1. In an aqueous electroless copper plating bath containing a source ofcopper ions, and a reducingagent capable of reducing said ions tometallic copper on the surface of an object immersed in said bath, theimprovement which consists in the presence of a stabilizing agent insaid bath, the stabilizing agent being present in said bath in an amountsufficient to substantially prevent spontaneous precipitation of copperin the absence of said immersed object, and being an organic seleniumcompound or selenide, diselenide, selenosulfate or selenocyanate of analkali metal, the selenium being present in said stabilizing agent inthe oxidation state minus one or minus two.

2. In bath according to claim 1, said stabilizing agent being present insaid bath in a concentration of approximately 0.001 to 0.300 gram perliter.

3. In a bath according to claim 1, said stabilizing agent being acompound selected from the group consisting of potassium-diselenide;

dipropyl diselenide;

di-n-butyl diselenide;

di-n-amyl diselenide;

di-n-hexyl diselenide;

di-n-heptyl diselenide; di-(2-3-dihydroxypropyl) diselenide;

di- (potassiumsulfopropyl) diselenide;

di- (potassiumsulfoethyl) diselenide; di-(sodiumsulfobutyl)diselenide;bis-(sodiumcarboxymethyl)diselenide; bis- (potassiumcarboxyethyl)diselenide; bis- (potassiumcarboxypropyl)diselenide; bis-(potassiumcarboxydecyl) diselenide; diphenyl diselenide;

di-p-tolyl diselenide; di-(p-methoxyphenyl)diselenide;

di- (p-nitrophenyl diselenide; bis-(o acetylphenyl)diselenide;di-2,2'-biphenylyl diselenide;

bis- (p-potassiumsulfophenyl) diselenide; bis- (p-chlorophenyldiselenide;

bisp-carb oxypheuyl) diselenide; diseleniumdiacetylurea;

dibenzyl diselenide;

di- N-phenyl-carbamoylmethyl) -dise1enide; bis- (p-nitrobenzyl)diselenide;

bisp-methylb enzyl) diselenide bis- (p-cyanobenzyl)diselenide;bis-(p-carboxy-benzl)diselenide;

bis- (p-bromobenzyl) diselenide; bis-(p-phenylethyl)diselenide;bis-(3-hydroxpropyl)diselenide; bis-(a-tetrahydrofurylmethyl)diselenide; bisp-phenoxyethyl) diselenide biscyclohexyl) diselenide;bis-(cyclopentyl)diselenide; potassiumselenosulfate;p0tassiumbenzylselenosulfate;

potassium p-nitrobenzylselenosulfate; potassiump-methylbenzylselenosulfate; potassiump-potassium-carboxybenzylselenosulfate; potassiump-methoxybenzylselenosulfate; potassium p-ethoxybenzylselenosulfate;potassium p-cyanobenzylselenosulfate; potassiump-ethyl-benzylselenosulfate; potassium p-bromobenzylselenosulfate;potassium ethylselenosulfate;

potassium butylselenosulfate;

potassium octylselenosulfate;

potassium dodecylselenosulfate; potassium1,3-dihydroxypropylselenosulfate; potassium hydroxyethylselenosulfate;potassium phenoxyethylselenosulfate; potassiumtetrahydrofurfurylselenosulfate; potassium phenylethylselenosulfate;potassium phenylpropylselenosulfate; potassium3-hydroxypropylselenosulfate; dipotassium w-carboxyethylselenosulfate;dipotassium w-carboxybutylselenosulfate; dipotassiumW-carboxydecylselenosulfate; dipotassium w-sulfoethylselenosulfate;dipotassium w-sulfopropylselenosulfate; potassiumcyclopentylselenosulfate; potassium selenide;

phenylseleniumacetic acid;

-, mor p-nitrophenylseleniumacetic acid; o-, morp-methoxyphenylseleniumacetic acid; o-, mofp-chlorophenylseleniumaceticacid; 3,4-dimethylphenylseleniumacetic acid;2,4-dimethylphenylseleniumacetic acid; benzylseleniumacetic acid;ethylseleniumacetic acid; seleniumdiacetic acid; seleniumdiproponicacid; seleniumdi'butyric acid; benzylseleniumbutyric acid;benzylseleniumundecanoic acid;

sodium ethylseleniumpropanesulfonate; bis- (sodium sulfopropyl)selenide; phenylseleniumglycolic acid;

sodium phenylseleniumpropanesulfonate; sodium benzylseleniumpropanesulfonate; bis- (phenoxyethyl) selenide; diphenylselenide;

dibenzylselenide;

difurfurylselenide; bis-p-methylphenylselenide;bis-p-nitrophenylselenide; bis-3-phenylpropylselenide; dipropylselenide;

bis- (hydoxyethyl) selenide; sodiumselenocyanate;potassiumselenocyanate;

o-, por m-nitrophenylselenocyanate;

o-, mor p-methylphenylselenocyanate; p-methoxyphenylselenocyanate;p-ethylphenylselenocyanate; p-ethoxyphenylselenocyanate;

sodium 4-cyanoseleno-phenylsulfonate; o-, morp-chlorophenylselenocyanate; 2-nitro-4-chlorophenylselenocyanate;p-carbmethoxyphenylselenocyanate; ethylselenocyanate;

butylselenocyanate;

decylselenocyanate;

potassium selenocyanoacetate;

potassium selenocyanopropionate; potassium selenocyanoundecanoate;

potassium selenocyanopropanesulfonate; potassiumselenocyanoethanesulfonate; pheiioxyethylselenocyanate;furfurylselenocyanate; benzylselenocyanate; phenylpropylselenocyanate;p-nitrophenyselenocyanate; fl-naphthylselenocyanate;phenylselenocyanate; carboxymethyldimethyl-selenoniumbromide;phenacyI-dimethyl-selenoniumbromide; dimethyl-selenetin dicarboxylicacid; triethylselenonium iodide; tribenzylselenoniumchloride;dimethyl-benzl-selenoniumbromide; triphenylselenoniumchloride; tri-ptolylselenoniumchloride.

4. In a method of depositing copper on a conductive surface or on anactivated'non-conductive surface of a body by immersing said body in abath containing a source of copper ions and a reducing agent capable ofreducing said ions to metallic copper on said surface of the, immersedbody, the improvement which consists in immersing said body in a bath asset forth in claim 1.

5, In a method of depositing copper on a conductive surface or on anactivated non-conductive surface of a body by immersing said body in abath containing a source of copper ions and a reducing agent capable ofreducing said ions to metallic copper on said surface of the immersedbody, the improvement which consists in immersing said body in a bath asset forth in claim 3.

References Cited UNITED STATES PATENTS 1/1956 OstroW 20452 4/1959 Foulke204-S2 US. Cl. X.R. 117130, 47,

